1. Field of the Invention
This invention relates to a dielectric device using dielectric properties and electrical-mechanical conversion properties.
2. Description of the Related Art
In the related art, a type of dielectric device using ferroelectric ceramics is known. The dielectric device using this ferroelectric ceramics can usually be obtained by forming a laminated structure, by patterning an electrode on a ferroelectric ceramic thin plate formed by the screen printing method or the green sheet method, or joining to another metal or a ceramic thin plate.
Here, the screen printing method is a method of obtaining a ceramic thin plate used as the base of a dielectric device by forming a film on a predetermined substrate from a slurry containing a ceramic powder dispersed in an organic binder by screen printing, and sintering this film at a high temperature of 900° C. or higher. The green sheet method is a method of obtaining a ceramic thin plate by forming a thick film of predetermined thickness from the aforesaid slurry, drying to obtain a green sheet, and sintering at a high temperature in the same way as above after hole-punching. In recent years, this kind of dielectric device has been used as an electron emitter, for example in field emission displays (FEDs) or electron beam sources in electron microscopes.
The electron emitter is operated in a predetermined vacuum level, and when a predetermined electric field is applied to the electron emission portions (hereafter, emitters), electrons are emitted from the emitters. When this electron emitter is used in an FED, plural electron emitters are arranged in two dimensions, and plural fluorescent bodies are respectively disposed at a predetermined interval from the electron emitters so as to correspond to the plural electron emitters. By selectively driving one of these plural electron emitters arranged in two dimensions at any desired position, electrons can be emitted from an electron emitter in any desired position, fluorescence can be emitted from a phosphor in any desired position due to collision between the emitted electrons and the phosphor, and a desired display can thus be obtained.
Some early examples of this electron emitter are given for example in the following Patent References 1 to 5. These electron emitters do not use the aforesaid dielectric device, but instead have an emitter which includes minuscule conductive electrodes with sharp tips. When a predetermined drive voltage is applied between a reference electrode opposite to this emitter and the emitter, electrons are emitted from the tips of the emitter. Therefore, to form this minuscule conductive electrode, microfabrication by etching, forming or the like is required. Also, to emit a predetermined electron amount into a predetermined vacuum level from the tips of the aforesaid conductive electrodes, a sufficiently high voltage is required as the drive voltage, and an expensive drive element which can supply a high voltage, such as an IC for driving this electron emitter, is required.
As stated above, the problem of the electron emitter using a conductive electrode as an emitter has been that the production costs of not only the electron emitter itself but also the device to which the electron emitter is applied increase. In recent years, therefore, an electron emitter using the aforesaid dielectric device, i.e., an electron emitter wherein the emitter is comprised of a dielectric, has been designed, as disclosed for example in the following Patent References 6 and 7. General knowledge on the electron emission in the case of using a dielectric as the emitter is disclosed in the following Non-Patent References 1 to 3.
The electron emitter disclosed in Patent References 6 and 7 is configured so as to: cover a part of the upper surface of an emitter including a dielectric with a cathode electrode; and dispose an anode electrode at a position on or below the lower surface of the emitter or a position apart from the cathode electrode at a prescribed interval on or above the upper surface of the emitter. That is, the electron emitter is configured so that the exposed surface portion, where neither a cathode electrode nor an anode electrode is formed, of the emitter exists on the upper surface side of the emitter in the vicinity of the outer edge of the cathode electrode
Then as the first step, voltage is applied between the cathode electrode and the anode electrode so that the cathode electrode has a higher potential, and the electric field formed by the applied voltage makes the emitter (the exposed portion in particular) get into a prescribed polarized state. Next as the second step, voltage is applied between the cathode electrode and the anode electrode so that the cathode electrode has a lower potential. At this time, primary electrons are emitted from the outer edge of the cathode electrode, the polarization of the emitter is reversed, the primary electrons collide with the exposed portion of the emitter where the polarization has been reversed, and thereby secondary electrons are emitted from the emitter (the exposed portion in particular). The secondary electrons fly toward a prescribed direction caused by a prescribed electric field applied from outside and thereby electrons are emitted from the electron emitter.    [Patent Reference 1] JP-A No. 311533/1989    [Patent Reference 2] JP-A No. 147131/1995    [Patent Reference 3] JP-A No. 285801/2000    [Patent Reference 4] JP-B No. 20944/1971    [Patent Reference 5] JP-B No. 26125/1969    [Patent Reference 6] JP-A No. 146365/2004    [Patent Reference 7] JP-A No. 172087/2004    [Non-Patent Reference 1] Yasuoka and Ishii “Pulsed Electron Source using Ferroelectric Cathode,” J. Appl. Phys., Vol. 68, No. 5, pp. 546-550, 1999    [Non-Patent Reference 2] V. F. Puchkarev, G. A. Mesyats “On the mechanism of emission from the ferroelectric ceramic cathode,” J. Appl. Phys., Vol. 78, No. 9, 1 Nov., 1995, pp. 5633-5637    [Non-Patent Reference 3] H. Riege “Electron emission ferroelectrics—a review,” Nucl. Instr. and Mech., A340, pp. 80-89, 1994